Slowed population growth could lower emissions by 29 percent

Running projections through an energy and economic growth model shows that …

To meet goals of reduced emissions, we may need to look no further than our own populace, according to a study published in PNAS. By analyzing a few different data sets and projections for population and emissions growth, a group of researchers found that a concerted effort to slow population growth could contribute as much as 29 percent of the emissions reductions needed to avert dangerous levels of climate change. They also found that a more urban population causes a significant increase in emissions, while an older one lowers emissions.

Most of the ideas being floated to address climate change involve things like renewable energy and greater efficiency, which have a direct impact on carbon emissions. From electric cars to solar power, many of these strategies face significant hurdles before they can have a serious impact on the climate.

Instead of many small changes, one group of scientists decided to take a look at how our emissions would drop if the entire world's population could be swayed into slowing its growth down. They ran population and emissions projects from the UN and the Intergovernmental Panel on Climate Change through an energy and economic growth simulation called the People-Environment-Technology (PET) model.

While investigating a lower population growth scenario sounds simple enough, it's not as easy as just cranking down the "people" knob in the PET session and watching the emissions graph plunge. The authors note that population, as well as how people are distributed and how old they are, directly and indirectly affect a lot of factors, including economic growth, labor supply, and savings and consumption behavior. Combined, all these factors can have a dramatic effect on emissions.

All of the scenarios the authors looked at involve emissions peaking at a higher level than they are at now. However, a modest emissions projection and a reduction in population growth from the UN's "medium" projection to the "low" one (just under 9 billion vs. 5.5 billion by 2100) would drop emissions by 5.1 gigatons of carbon per year.

The simulation also showed that a population that is front-loaded with old people, especially in industrialized regions, resulted in the biggest reduction in emissions. An aging population, because of the reduced labor and resulting slower economic growth, could contribute to as much as a 20 percent reduction in emissions.

An unexpected find was that an increase in urbanization could contribute to a large rise in emissions, by more than 25 percent. Again, this was a result of the relationship between labor and the economy—workers in urban areas are more productive and create more economic growth, and therefore more emissions. While urban area dwellers tend to have smaller carbon footprints in terms of lifestyle, their economic actions turn out to significantly outweigh that benefit.

The authors note that, because of its economic influence, changes in the US's population had some of the most pronounced effects on emissions. The total impact of changes in US demographics didn't outweigh the change that could result from slowed growth in China and India, but the reductions per capita were some of the largest.

While a total possible 29 percent reduction in emissions sounds great, the whole exercise is pretty firmly idealistic. Governments can't order everyone to disband their cities and start getting older faster; at least, the authors note this would not be the wisest of policy choices (though they could always secretly put something in the drinking water).

However, the authors note that a push for family planning may at least help do the trick: many countries have unmet family planning needs, and implementing them could reduce fertility by about 0.2 births per woman in in US, and by 0.6-0.7 births per woman in developing countries.

Casey Johnston
Casey Johnston is the former Culture Editor at Ars Technica, and now does the occasional freelance story. She graduated from Columbia University with a degree in Applied Physics. Twitter@caseyjohnston

Actually, I'm sort of for slowing down the pop growth. There's a lot of wasted manpower sitting around poor and impoverished. That's wasted resources. Until we learn to better utilize the population we have, we should probably avoid cranking out more. But, try telling that to the welfare mother in a trailer park living off food stamps with 5 kids from 4 different fathers.

I don't think family planning will be of much help in third-world countries. If I'm processing what Hans Rosling's delivers in his speeches properly then the issue is that first-world countries tend to have 1 child per couple and third world countries tend to have 4+. The reason appears to be directly related to infant mortality and quality of life. People, and infants, are more likely to die earlier due to environmental or political conditions that we in the first word are not subjected to.

To put it bluntly, if all third-world countries had the same quality of life as we do then they would start having just 1 child per couple as well.

To put it bluntly, if all third-world countries had the same quality of life as we do then they would start having just 1 child per couple as well.

Yes. To the posters above, stop portraying the third world in a poor light. Basically, what has been seen to happen is that as long as it is beneficial to have lots of children (help with labour) people will continue to have them. If its not beneficial (expensive to raise) people will stop. So when developing economies change, they too will curb growth rates.

Anyway, projections show that the population will peak around 2050 at 11.5 billion and start to decline. Population decline brings economic and job pains however. (Japan, Russia, etc). When you have lots of young people in the work force your economy is productive and its easy to pay for medical care and pensions. When the ratio gets skewed you are pretty fucked. This will be the future challenge. Not perenially growing population.

On the correlation between age and resource usage, when a person is young with a young or growing family they are earning a lot and spending it to build their life. As you get older you slow this spending down.

How about a simulation where a large portion of population would move off the planet (Earth), to some other planet (Mars, etc... whatever).This kind of perspective could allow us to refocus - instead of targeting how to exploit as much of resources (energy, food, minerals) here on the Earth, we'd suddenly be allowed to grasp the bigger picture and move on. It's about time that we all realize, that fighting for resources on Earth has many undesirable side-effects, like wars, inequality, etc.Excessive usage of those resources (we believe) is responsible for global warming.So, why keep thinking small and just piling-up problems?Making a big step of moving off our planet is not a job for one country, but it requires participation of the whole planet. Instead of having a large portion of population "stuck" in negative enterprises (war, hate, boredom,...), we could mobilize them in doing something for a global good and eventual expansion beyond our globe.Yes, at this point such thinking may seem ridiculous, but so did ideas of flying to the Moon about a century ago, or, say, idea of having internet access on your mobile phone in 1980's (when mobile phones did not exist yet and the internet was like a pie-in-the-sky).So much changed in just last 20 years, therefore setting currently unachievable goal for the next generation isn't like a big deal.

What amazes me is the lack of logical thinking at most people. Consider this:

We burn fossil fuels right? What is a fossil fuel, coal or oil? It is the remaining of organic organisms (mainly trees, bushes etc. ). So let's ask ourselves, where did those trees from the past got their CO2 ? The plants have always been "converting" CO2 from the air to stuff they need so they work today as they've been working in the past. So logically thinking we come to conclusion that there MUST have been A LOT more CO2 than today since there were so many trees that "created" all this coal and oil. And taking that into fact the excess of CO2 didn't "boil" the planet, what's more!! Looking at how much coal and oil there is we must say that it was good!!

So i would stop preaching all this CO2 crap (that's used ONLY as an argument/justification to decrease consumption of goods), we should consider consuming less BUT not making it possible for some shills to earn enormous money on that CO2 scam!!

How about a simulation where a large portion of population would move off the planet (Earth), to some other planet (Mars, etc... whatever).

Still, this would be more expensive and difficult by orders of magnitude when compared to something like making parts of the deserts or tundra more habitable.

As much as I am for the idea of not having all eggs in one basket and starting the long, slow process of developing the tech needed to move past the Earth, I wouldn't imagine that it's the most efficient way to solve the issues listed in this article.

We burn fossil fuels right? What is a fossil fuel, coal or oil? It is the remaining of organic organisms (mainly trees, bushes etc. ). So let's ask ourselves, where did those trees from the past got their CO2 ? The plants have always been "converting" CO2 from the air to stuff they need so they work today as they've been working in the past. So logically thinking we come to conclusion that there MUST have been A LOT more CO2 than today since there were so many trees that "created" all this coal and oil.

No, it means that the CO2 was captured over a longer period of time than it is taking for us to burn it. CO2 isn't an immutable compound. There isn't a fixed amount of CO2 that has been here from the beginning of time, originally in the air and then slowly captured as the hydrocarbons that are currently in the ground. The CO2 that historic plants captured was created by the respiration of historic animals (among other things). The animals here today continue to convert oxygen into CO2, and on top of that we are releasing additional CO2 by burning hydrocarbons created in the past.

So i would stop preaching all this CO2 crap (that's used ONLY as an argument/justification to decrease consumption of goods), we should consider consuming less BUT not making it possible for some shills to earn enormous money on that CO2 scam!!

While I agree, you do have to make a distinction between coal and liquids. Coal cannot be refined and its burning releases heavy metals and other toxins. Refined petrol is just fine though.

We are entering an age where the green movement is falling apart. We are being asked to cut back in addition to recycling, but all that is moot in the face of 3rd world industrialization and population advances.

We need to focus on toxins - real toxins, not co2 - like heavy metals, MTBE, nutrification of run off, etc. which have drastic impacts today. Not minuscule impacts 100 years from now.

It has been proven that population increase corelates with the wealth of that population. Unfortunatelly the rich countries are rich thanks to "developing" countries and in order to stay rich the rich countries MUST ensure that poor countries stay that way. Otherwise that house of cards will fall. That is why they want to decrease population in developing countries because our "rich" population is already aging and then will start decreasing.

What amazes me is the lack of logical thinking at most people. Consider this:

We burn fossil fuels right? What is a fossil fuel, coal or oil? It is the remaining of organic organisms (mainly trees, bushes etc. ). So let's ask ourselves, where did those trees from the past got their CO2 ? The plants have always been "converting" CO2 from the air to stuff they need so they work today as they've been working in the past. So logically thinking we come to conclusion that there MUST have been A LOT more CO2 than today since there were so many trees that "created" all this coal and oil. And taking that into fact the excess of CO2 didn't "boil" the planet, what's more!! Looking at how much coal and oil there is we must say that it was good!!

So i would stop preaching all this CO2 crap (that's used ONLY as an argument/justification to decrease consumption of goods), we should consider consuming less BUT not making it possible for some shills to earn enormous money on that CO2 scam!!

You are right. We could have a lot more CO2. And the earth would be fine. Our place on it, with the need to support the kind of population we have (and might have), might be a bit suspect though.

I fully agree BUT as i wrote above we need to allow the poor countries be dirty because that is the only way they will get out of poverty, if we would impose limits on them they will stay poor for decades.

So i would stop preaching all this CO2 crap (that's used ONLY as an argument/justification to decrease consumption of goods), we should consider consuming less BUT not making it possible for some shills to earn enormous money on that CO2 scam!!

While I agree, you do have to make a distinction between coal and liquids. Coal cannot be refined and its burning releases heavy metals and other toxins. Refined petrol is just fine though.

We are entering an age where the green movement is falling apart. We are being asked to cut back in addition to recycling, but all that is moot in the face of 3rd world industrialization and population advances.

We need to focus on toxins - real toxins, not co2 - like heavy metals, MTBE, nutrification of run off, etc. which have drastic impacts today. Not minuscule impacts 100 years from now.

This is one of the more frustrating things I hear.

Generally (but I have no idea your position), people against inaction first say that it's not true.

Then they quickly move on to it's hopeless anyway, because of India and China.

This result is one of those "true but pointless" observations. The best way to decrease population growth is to increase economic prosperity. All the developed countries in the world have seen decreased population growth, regardless of culture. This is probably because when people have the freedom to do more things with their lives they start seeing large families as impeding these goals, but nevermind the reason the result is the same. The best way to decrease population growth is to turn developing countries into developed countries, and to do that you need energy. Lots of it. The only solution to this is economical clean energy sources.

Once we get CO2 output down to a reasonable level, then we still have the problem of how to keep it there. Reduced population growth can help with that. Assuming we fix our immediate problems with global warming, then this will be a part of our grandchildren' solution to the long term problem.

The plants have always been "converting" CO2 from the air to stuff they need so they work today as they've been working in the past. So logically thinking we come to conclusion that there MUST have been A LOT more CO2 than today since there were so many trees that "created" all this coal and oil.

As another commenter pointed out, that CO2 was captured over millions of years and we are re-releasing it over 2 centuries. That's a significant shift in CO2 concentration in a very short amount of time, relatively speaking.

BenderBendingRodriguez wrote:

So i would stop preaching all this CO2 crap (that's used ONLY as an argument/justification to decrease consumption of goods), we should consider consuming less BUT not making it possible for some shills to earn enormous money on that CO2 scam!!

Who are these people making "enormous money" on a CO2 scam? Name names or stop spreading FUD. The only parties that I see making enormous money are the oil companies.

So in the end it is about economic growth. Well either we are fucked, or it will fix itself soon as we are running out of ways to make the economy continue to grow (spreading the existing economy to india and china will have a temporary effect at best).

I base this one the explosion in paper "investments" like the recent CDO mess. If there had been real investment options people would be more likely to avoid these multi-tiered derivatives. But as there is not, the only option left for the economists eternal 3% global economic growth is by piling on the derivatives. End result is a cake that becomes sliced thinner and thinner, while each slice gets a higher and higher price as the entity doing the slicing requests a brokers fee.

But some of the comments are interesting. We are working against some pretty fundamental elements of our nature in trying to prevent cataclysm.

1) Our greed is insatiable.

2) We are inherently self centred, shortsighted, and not rational.

3) Procreation (like religion) is hardwired.

I'm not saying any of the above are ipso facto bad, they all serve their functions in terms of helping to increase the reproductive success of individuals.

Given the ad hoc nature of our brains and that there is no rational central command, attempting to use logic and science to organize society and individual lives while preserving rights, freedoms, and democracy to prevent cataclysm will never work. People will act and behave according to their natures which are greedy, irrational, and self centered; and because of this our population will be limited the old fashioned way-- carrying capacity and diminution of resources. The idea that we can bring 7-12 billion people up to the standard of living in Europe or America and thereby reach a steady state of sustainable population is wishful thinking. And even if it were possible, people will always want more stuff.

Whether we are here or not, liife will not cease on the planet. I wonder if we will birth a successor species before we go, either through genetic engineering of our own code, or possibly a type of silicon intelligence. Maybe their nature will be more rational and less greedy than ours and they will last more than a few hundred thousand years, or how ever long homo sapien spaiens have been around.

This idea that we need to take concerted efforts to slow population growth is grossly irresponsible. Human beings are very adaptable and I find the idea that we cannot bring everyone up in this world to a first world standard of living incredibly lacking in optimism and lacking in hindsight given that state of human condition a 100 years ago compared to now. If you pay attention to the changes in demographic trends population growth rates are dropping world wide already, in both developed and developing nations, naturally. Raising children is expensive in developed societies and as the rest of the world develops population birth rates have slowed now. A slower growth rate of humanity, or a stable population, is much more manageable when it comes to resource consumption and infrastructure maintenance, however, in the future if steps aren't taken the human population could start decreasing, which in itself possess dire ramifications for future prosperity as we lack the human capital to maintain infrastructure, economic growth, and fund our welfare system that cares for the elderly.

As another commenter pointed out, that CO2 was captured over millions of years and we are re-releasing it over 2 centuries. That's a significant shift in CO2 concentration in a very short amount of time, relatively speaking.

The nature produces FAR FAR more CO2 than humanity combined from all ages. Another interesting thing is the medieval times where it was hotter than even right now (vikings lived on greenland!! and that's why it is called like that!) and i really doubt they were producing so much CO2 back then. Next interesting thing that is often omitted is the fact that ALL the planets in our solar system are getting hoter!! Explain that!!

Quote:

Who are these people making "enormous money" on a CO2 scam? Name names or stop spreading FUD. The only parties that I see making enormous money are the oil companies.

You don't have to look far, Al gore is one of the people that would benefit from that as he already earned millions of dollars trading CO2. So i wouldn't trust someone who is in fact a beneficiary of any gloabal changes.

So let me get this straight. We can manage global emissions by being less economically productive, having fewer young people, and building smaller cities. GREAT! I only believe it because the truth is usually pretty depressing. And it's only Monday.

So let me get this straight. We can manage global emissions by being less economically productive, having fewer young people, and building smaller cities. GREAT! I only believe it because the truth is usually pretty depressing. And it's only Monday.

No, bigger cities. The problem with cities was that the emissions related to productions increases from stacking the workers tightly closer to their workplace outweighed the reduction in having them commute to work.

So each worker commuting results in say 1 emission unit, and 1 unit from work, the removal of commute resulted in at least a 1.5 unit increase from the extra work time and such made available.

The nature produces FAR FAR more CO2 than humanity combined from all ages.

Since about 1750, it has been the reverse. The IPCC report very, very conservatively assumes that human activity only accounts for ~50% of atmospheric CO2 concentrations going forward, to leave room for as-yet undiscovered carbon sinks that may appear with increased concentrations.

What do you think they have wrong?

Quote:

Another interesting thing is the medieval times where it was hotter than even right now (vikings lived on greenland!! and that's why it is called like that!) and i really doubt they were producing so much CO2 back then.

The Medieval Warm Period was ~0.2 deg C warmer than now, and that is consistent with models of interglacial cycles. However, it is the same models validated against these inputs that predict significant warming due to anthropogenic CO2 emissions.

What do you think is wrong with these models?

Quote:

Next interesting thing that is often omitted is the fact that ALL the planets in our solar system are getting hoter!! Explain that!!

That's interesting -- citation please! Do you think this accounts for the entirety of the rapid 20th century warming trend? Why or why not?

Yet the economists will tell us slowed population growth is bad for the economy, so bad that immigration must increase to ensure a strong future economy.

I guess this is true when crass consumerism is rampant. Perhaps society should focus its attention elsewhere?

It's not really consumerism you have to worry about. An ageing population (this is more important than there simply being a declining population, as if people are being picked off by sharpshooters, proportionately, across age demographics) results in the death of your labour force, a decline in entrepreneurship and a swell in the pension system. It's difficult enough for western nations in the post-globalism age without labour being (more) expensive due to both a scarcity of workers and having to offset tax liabilities to keep the olds comfortable and healthy.

BenderBendingRodriguez wrote:

You don't have to look far, Al gore is one of the people that would benefit from that as he already earned millions of dollars trading CO2. So i wouldn't trust someone who is in fact a beneficiary of any gloabal changes.

Christ, you haven't even bothered to look into the issue, if the only person you can name is a retired politician and environmental advocate. And where, exactly, has he been earning, "millions of dollars trading CO2"? He's involved with venture capital and R&D, investing into technologies pertinent to dealing with climate change. Imagine that: someone who is advocating cleaner technology is also putting their money where their mouth is. That must be why he's an advocate! It's not as if he's been advocating for the environment since the 70's, or anything... oh wait.